function post(url, post_data, callback, err_back, asy) {
    if (err_back == null) {
        err_back = function (xhr, type, exception) {
            console.error(xhr);
            console.error(type);
            console.error(exception);
            alert("交易超时");
        };
    }
    post_data = JSON.stringify(post_data);
    $.ajax({
        url: url,
        type: 'POST',
        // contentType: "text/html;charset=utf-8;",
        contentType: "application/json;charset=utf-8",
        data: post_data,
        async: asy || true, //false
        dataType: 'json',
        timeout: 6000 * 10,
        crossDomain: true,
        beforeSend: function (xhr) {
            xhr.setRequestHeader("Access-Control-Allow-Origin", "*");
            xhr.setRequestHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS");
        },
        success: callback,
        error: err_back
    });
}